Tamper proof closures have been widely utilized by packers of food, beverage and liquor items in recent years to provide an indication to the final purchaser as to whether the closure provided on the package, has been previously removed. A cloure that is applied by threaded engagement with the container neck is particularly susceptible to tampering. Any person passing through a super market could quickly pick up such a container, remove the closure, sample a portion of the contents and then replace the closure. The tampering problem is common to foods, soft drinks, and liquors. Generally, the more expensive the product, the more likely is the possibility that the container will be subjected to tampering.
Insofar as narrow neck containers are concerned, an aluminum shell type closure has been utilized heretofore to provide a tamper proof feature. Such shell is formed with a generally cylindrical skirt portion which is then subjected to a cutting operation to cut a series of peripherally extending slots in a medial portion of the skirt sidewall. The skirt sidewall is then applied to the container neck in conventional fashion by roll forming the threads in the closure sidewall and concurrently deforming the extreme bottom portion of the panel to engage underneath a peripherally extending external rib on the bottle neck to lock the bottom panel portion to the container. Any subsequent attempt to remove the closure by unscrewing it from the container neck results in the severance of the bridges which constitute the uncut portions of the panel skirt remaining after the aforementioned cutting operation.
Attempts have heretofore been made to provide the same type of construction in a molded plastic closure. All of such prior art attempts have been in the direction of producing the molded slots and bridges in the closure during the original closure molding operation on the theory that forming the complete closure in one operation was the less expensive route to follow. This has not proven to be the case, however. To incorporate the annular series of slots interspaced by bridges in the molded closure, a complex mold has to be provided, thus greatly increasing the mold costs for producing such closures. Furthermore, due to variations that are inherent in the closure molding process when an attempt is made to form very small segments of plastic interconnecting larger segments, the size and strength of the resulting bridges varied substantially, thus, providing noticeable variations in the shearing strength of the bridges thus produced. Lastly, if conventional applicating machines were to be used, the bridges had to be sufficiently large to not sever when forcing the retaining rib over the container neck bead during application of the closure.